The purpose of this proposed study is to investigate the control of insulin and glucagon release in the fetus and neonate. The isolated rat pancreatic islet will be used initially as a model system. Islets from animals of different ages, from fetus to adult, will be incubated in the presence of substances known to stimulate the release of insulin and glucagon in the adult animal. Induction of a mature pattern of insulin and glucagon response will be attempted by chronic exposure of the fetus and neonate to these various stimuli. It is expected that pancreatic islets of fetal and neonatal animals of other species, including primates, will also be studied. In addition, an attempt will be made to develop a specific antibody for pancreatic glucagon for use in whole animal studies. Information derived from this investigation should shed light on the nature of carbohydrate homeostasis in newborn specifically and on the nature of control of pancreatic endocrine function in general.